Tenda 3G622R+, Руководство пользователя

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3G 11N Wireless Router
9.3 ALG Service Settings
In the context of computer networking, an ALG or
application layer gateway consists of a security
component that augments a firewall or NAT employed in
a computer network. It allows customized NAT traversal
filters to be plugged into the gateway to support
address and port translation for certain application layer
"control/data" protocols such as FTP, BitTorrent, SIP,
RTSP, file transfer applications etc.
In order for these protocols to work through NAT or a
firewall, either the application has to know about an
address/port number combination that allows incoming
packets, or the NAT has to monitor the control traffic
and open up port mappings (firewall pinhole)
dynamically as required. Legitimate application data
can thus be passed through the security checks of the
firewall or NAT that would have otherwise restricted the
traffic for not meeting its limited filter criteria.
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